Add missing null check when unloading partition manager (#5817)
## What changed?
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Fix panic when the partition being unloaded is not found in the map.
## Why?
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## Documentation
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5709cbf...
by
Temporal Data <email address hidden>
Fix schedule workflow to CAN after signals (#5799)
## What changed and why?
If a schedule was paused and received a large number of signals
(trigger, backfill, etc.), it wouldn't be able to continue-as-new and
history size could grow past the suggested limit.
For various reasons the main loop receives and processes signals across
iterations, with checking for CAN in between, so a wakeup due to a
signal (instead of a timer) would prevent CAN. Refactoring is hard due
to the determinism requirement, so the simplest fix is to do a second
check.
